KR910007458B1 - Process for reclaiming polyethylene terephthalate scrap contaminated with chlorine - contrining polymer and optically anisotropic melt forming aromatic copolymers based on t - butyl - 4 - hydroxybenzoic acid - Google Patents

Abstract

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Description

Methods for recovering and reusing PET scrap materials, compositions comprising PET scrap materials and products obtained with the compositions

The present invention relates to methods for the recovery and reuse of polyethylene terephthalate (PET) scraps coated with chlorine-containing polymers, as well as to useful products made of such recovered materials.

For example, there is a large amount of PET scrap available for industry for reuse from sources such as PET bottles, fibers and films. Some PET films and bottles that require more impermeability to oxygen and water are coated with a thin layer of chlorine-containing polymer, making it difficult to use substantial amounts of scrap. The chlorine-containing polymer is usually a copolymer of vinylidene chloride with a small amount of vinylidene chloride homopolymer or other vinyl comonomer (about 0.1-10% by weight), which may or may not be chlorinated by itself. The nomenclature of these additional comonomers can vary from manufacturer to manufacturer and is usually considered entirely by the film coating industry. Furthermore, copolymers of polyvinyl chloride and vinyl chloride with small amounts of other unsaturated monomers can be used for the coating application. In addition, the chlorine-containing polymer is coated on the photographic polyester film substrate for adhesion. When vinylidene chloride polymer is used as the coating material, the amount of this coating is usually about 0.01-0.24% by weight of the total coated polymer weight. However, this amount is not critical and can be adjusted appropriately for the particular application. Ordinary scrap materials consisting of PET coated with chlorine-containing polymers cannot be used as they are and must be terminated with sodium hydroxide or subjected to other chemical treatments to remove the polymer coating. For example, vinylidene chloride polymer degrades at about 200 ° C. below the normal PET processing temperature. If scrap PET containing vinylidene chloride polymer is used inadvertently in the process, hydrogen chloride is released, causing decomposition and discoloration of the PET and corroding the equipment. This technique does not describe any implementation of the melting process that allows the use of vinylidene chloride polymer or PET scraps contaminated with vinyl chloride polymer without first completely removing chlorine-containing polymer contaminants.

Therefore, it is easy to see that the process of recovering and reusing millions of kilograms of PET scrap material each year is of great industrial interest.

으로부터 형성된 라디칼로서, 에틸렌 공중합체의 약 0-40중량%, 바람직하게는 15-35중량%, 가장 바람직하게는 20-35중량%를 구성하고 : Y는 공중합성 불포화 유기산의 에폭시 에스테르, 공중합성 비닐 또는 알릴기를 갖는 에폭시에테르, 및 탄소수 4-12의 모노에폭시-치환 디올레핀으로 구성된 군으로부터 선택된 에폭시기-함유 공중합성 단량체로서, 에틸렌 공중합체의 약 0.5-20중량%, 바람직하게는 2-10중량%, 가장 바람직하게는 3-8중량%를 구성한다.According to the invention, a scrap material of polyethylene terephthalate coated with a chlorine-containing polymer is combined with about 5-25% by weight of ethylene copolymer E / X / Y based on the weight of the scrap material and the bound polymer material A method of recovering and reusing a scrap material of polyethylene terephthalate coated with a chlorine-containing polymer, comprising melt-mixing at a temperature of about 260-310 ° C., in which E is Is a radical formed from ethylene and constitutes about 40-99.5% by weight of the ethylene copolymer: X is R ₁ an alkyl group having 1-8 carbon atoms, preferably 4-6 carbon atoms, most preferably 4 carbon atoms and R ₂ Is hydrogen, methyl or ethyl, preferably hydrogen or methyl, most preferably hydrogen

As radicals formed from, it constitutes about 0-40%, preferably 15-35%, most preferably 20-35% by weight of the ethylene copolymer: Y is an epoxy ester of a copolymerizable unsaturated organic acid, copolymerizable Epoxy group-containing copolymerizable monomer selected from the group consisting of an epoxy ether having a vinyl or allyl group, and a monoepoxy-substituted diolefin having 4-12 carbon atoms, about 0.5-20% by weight of the ethylene copolymer, preferably 2-10 Weight percent, most preferably 3-8 weight percent.

If the physical and mechanical properties of the ethylene copolymer are not altered inherently, minor amounts may be present as additional comonomers such as CO and methyl acrylate. It is unlikely to be effective below the lower limit of the ethylene polymer range, while values above the upper limit of the range are expected to result in excessive crosslinking of the system.

Preferred comonomer Y is selected from the group consisting of glycidyl methacrylate and glycidyl acrylate, with preferred ethylene copolymers E / X / Y being an ethylene / n-butyl acrylate / glycidyl methacrylate terpolymer. to be.

The ethylene copolymers used in the process of the invention can be prepared by direct copolymerization, ie by copolymerizing ethylene, epoxy group-containing monomers Y and comonomer X, if present, at elevated temperatures and pressures in the presence of free-radical polymerization initiators. The polymerization temperature is preferably about 100-270 ° C., most preferably 130-230 ° C. The polymerization pressure is usually higher than about 70 MPa, but is preferably in the range of 140-350 MPa.

Copolymers of this kind as well as the above copolymerization methods are generally known or described in British Patent No. 1,352,088 of Sumitomo Chemical Company, Ltd. In addition to the E / X / Y copolymer, the polymer mixture may contain a small amount of low modulus reinforcing polymer of about 5-25% by weight based on total polymer weight. Suitable reinforcing polymers are described in US Pat. No. 4,172,859 to Epstein. Typical reinforcing polymers include, for example, the following alternating copolymers or random copolymers: ethylene / isobutyl acrylate / methacrylic acid terpolymers: ethylene / methyl acrylate / monoethyl maleate terpolymers and their 0-100% neutralized zinc, sodium, calcium, lithium, antimony and potassium salts: and ethylene / vinyl acetate / carbon monoxide terpolymers.

Scrap from PET coated with vinylidene chloride polymers and similar chlorine-containing polymers can be processed, for example mixed, extruded or injection molded at the same temperature as pure PET resin, ie 270 ° -310 ° C. That is a thermoplastic material. In general, PET scrap derived from commercial grade PET resin can be used. Mixing of the scrap material may be carried out in any suitable commercial apparatus such as an extruder or mixer, but it is desirable to maintain the extruder at barrel temperature so that the polymer material can be heated to a melting temperature of about 260-310 ° C.

Very surprisingly, a mixture of scrap materials of PET coated with a chlorine-containing polymer was mixed with an ethylene copolymer E / X / Y according to the above definition and the mixture melted into a common polymer such as an extruder or an injection-molding apparatus. When produced in process equipment, the destruction and / or discoloration of PET polymers and the corrosion of the device are much reduced. The resulting manufactured products have acceptable mechanical properties and excellent barrier properties inherent in PET for many applications. They are therefore suitable for films as well as for commercial use, for example various types of containers and especially cans for solvent-based paints.

Furthermore, other additives such as calcium carbonate, calcium stearate, stearates of other metals or hydrotalcite may be added to the mixture with the E / X / Y copolymer at about 0.05-1.0% by weight of the scrap material. In the case, it has been found that significant additional improvements can be made. Other stearic acid metals can be used as lubricants, soaps and the like or can be any metal stearate commonly available, such as zinc stearate, aluminum stearate, sodium stearate, potassium stearate and the like. Hydrotalcite has the formula Mg ₆ Al ₂ (OH) ₁₃ CO ₃ . It is a natural mineral with 4H ₂ O. Instead of natural hydrotalcite, synthetic products with slightly different formulas Mg _4.5 Al ₂ (OH) ₁₃ CO _3. 3.5H ₂ O can be used in the same manner. The synthetic material can be purchased from Koiwa Chemical Industries Co., Ltd. under the name DHT-4A (Osaka, Japan). Natural or synthetic hydrotalcites can be calcined as needed to remove crystalline water.

The invention will now be described by the following examples of its preferred embodiments, where all parts, proportions and percentages are by weight unless otherwise indicated.

Example 1

PET scrap was made from PET having an intrinsic viscosity of about 0.58 as measured in a solution of a 60:40 phenol / tetrachloroethane mixture, some of which were covered with a layer of vinylidene chloride polymer. The amount of vinylidene chloride copolymer is such that the chlorine content of the coated scrap material is 320 ppm.

The film is cut into small plaques, mixed with another second polymer, extruded through a Warnerfryer twin screw extruder equipped with a stranding die, and the strands are pelleted for further processing. Cut with. Make vent holes in the extruder. The melting temperature of the polymer is about 280 ° C. The pellets obtained from this step are injection molded into a tumbler or tensile test bar at a molding temperature of about 40 ° C. The tumbler is 94 mm high, 56 mm in diameter at the bottom, and 70 mm in diameter at the top. The thickness of the bottom as well as the side walls is 1.6 mm. Standard size test bars for this test are 3.2 mm (1/8 in) thick and are tested under ASTM D256 standard conditions.

Other polymers mixed with PET scrap materials include ethylene / n-butyl acrylate / glycidyl methacrylate (67: 28: 5) copolymer (EBAGMA) or ethylene / n-butyl (74:26) acrylate aerials. Copolymer (EBA), and ethylene / n-butyl (74:26) acrylate copolymer (EBA) is not within the scope of the present invention. The toughness of the injection molded tumbler is measured using an instrument impact tester (modified Gardner impact) at the bottom of the tumbler. Measurements are made at 40 joules of impact energy using an impact penetrating shaft of 1.25 cm diameter and a spherical point of 6 mm radius. The sample is destroyed by the full penetration of the impactor which requires less energy than the impact energy. The results are summarized in the table below.

Toughness is considered acceptable for instrument impact values greater than 1.0 joule in this type of experiment. However, preferred embodiments of the present invention include operating under reduced pressure, where the extruder vent holes are connected to a vacuum source rather than to the atmosphere. Under these conditions, much larger impact values can be expected and one joule is considered poor. From the experiments in this example, when working with vinylidene chloride-containing PET scrap material, 15-25% EBAGMA provides satisfactory toughness while 15-25% E / BA does not provide such toughness. It can be seen that. Uncoated PET could be satisfactorily processed in both cases.

Example 2

In another set of tests where test bars were made, when the extruder process stabilized (about 15 minutes), the gas exiting the vent holes of the extruder is passed through two absorption traps containing 0.1 N sodium hydroxide. These gases, in each case, pass through two traps forming a bubble for 25 minutes.

The chlorine content is then analyzed by chromatography on those contained in the traps.

In practice within the scope of the present invention, EBAGMA is mixed with vinylidene chloride polymer-containing PET scrap at a level of 20%. In a control example, the same scrap material is mixed with the E / BA copolymer at the same level. In both cases, the chlorine content in the PET scrap was 660 ppm. The test results are shown in the table below.

The increase in toughness and the substantial reduction in chlorine released are indicative of the effectiveness of EBAGMA in stabilizing the system.

Example 3

The process of Example 1 is followed except that the vent holes of the extruder used to make the pellets are connected to a vacuum source and operated at a reduced pressure of about 10 KPa. In the first run no additives are present in the mixture of PET scrap and EBAGMA. In the second run, a small amount of calcium stearate (industrial grade, Fisher Scientific, Inc) was added to the mixture, and in the third run, a small amount of DHT-4A (Koiwa Chemical Industries, Ltd) was added. In all implementations, the PET scrap material includes vinylidene chloride polymer in an amount such that the total chlorine content is 320 ppm. The results are described in the table below.

(a) calcium stearate

(b) synthetic hydrotalcite

It can be seen that even when there is no additive, significantly higher impact strength is obtained when pelleting under reduced pressure than when vented at atmospheric pressure (see Example 1). This improvement is further enhanced by adding calcium stearate or hydrotalcite to the mixture.

Claims (33)

The scrap material of polyethylene terephthalate coated with chlorine-containing polymer is combined with 5-25% by weight of ethylene copolymer E / X / Y based on the weight of the scrap material and the bound polymer material is 260-310 ° C. A method for recovering and reusing scrap material of polyethylene terephthalate coated with a chlorine-containing polymer, comprising melt-mixing at a melting temperature. In the above formula E / X / Y, E is a radical formed from ethylene and constitutes 40-99.5% by weight of the ethylene copolymer: X is R ₁ is an alkyl group having 1-8 carbon atoms, R ₂ is hydrogen, methyl or Ethyl

As radicals formed from 0-40% by weight of the ethylene copolymer: Y is an epoxy ester of a copolymerizable unsaturated organic acid, an epoxy ether having a copolymerizable vinyl or an allyl group, and a monoepoxy-substituted diolefin having 4 to 12 carbon atoms An epoxy group-containing copolymerizable monomer selected from the group consisting of 0.5-20% by weight of the ethylene copolymer. The method of claim 1, wherein R ₁ comprises 4-6 carbon atoms. The method of claim 2, wherein R ₁ comprises four carbon atoms. The method of claim 1 wherein Y is selected from the group consisting of glycidyl acrylate and glycidyl methacrylate. The method of claim 4 wherein the ethylene copolymer is a copolymer of ethylene, n-butyl acrylate and glycidyl methacrylate. The method of claim 1, wherein R ₂ is hydrogen or methyl. The method of claim 6, wherein R ₂ is hydrogen. The process of claim 1 wherein X comprises 15-35% by weight of the ethylene copolymer. The method of claim 8 wherein X comprises 20-35% by weight of the ethylene copolymer. The method of claim 1 wherein X is absent. The method of claim 1 wherein Y comprises 2-10% by weight of the ethylene copolymer. The method of claim 11, wherein Y comprises 3-8% by weight of the ethylene copolymer. The additive of claim 1 wherein the additive selected from the group consisting of calcium carbonate, calcium stearate, stearic acid salts of other metals and natural and synthetic hydrotalcite is initially present in the mixture at 0.05-1.0% by weight based on the weight of the scrap material. Way. The method of claim 1, wherein the low modulus reinforcing polymer is initially present in the mixture at 5-25% by weight based on the total polymer weight. A polymer blend composition consisting essentially of a scrap material of polyethylene terephthalate coated with a chlorine-containing polymer, melt-mixed with 5-25% by weight of ethylene copolymer E / X / Y, based on the weight of the scrap material. In the above formula E / X / Y, E is a radical formed from ethylene and constitutes 40-99.5% by weight of the ethylene copolymer; X is R ₁ is an alkyl group having ₁ to 8 carbon atoms and R ₂ is hydrogen, methyl or ethyl

As a radical formed from R 1, constitutes 0-40% by weight of an ethylene copolymer: Y is an epoxy ester of a copolymerizable unsaturated organic acid, an epoxy ether having a copolymerizable vinyl or an allyl group, and a monoepoxy-substituted di-carbon having 4-12 carbons. Epoxy group-containing copolymerizable monomer selected from the group consisting of olefins, which constitute 0.5-20% by weight of the ethylene copolymer. The composition of claim 15, wherein R ₁ comprises 4-6 carbon atoms. The composition of claim 16, wherein R ₁ comprises four carbon atoms. The composition of claim 15 wherein Y is selected from the group consisting of glycidyl acrylate and glycidyl methacrylate. 18. The composition of claim 17, wherein the ethylene copolymer is a copolymer of ethylene, n-butyl acrylate and glycidyl methacrylate. The composition of claim 15, wherein R ₂ is hydrogen or methyl. The composition of claim 20, wherein R ₂ is hydrogen. The composition of claim 15 wherein X comprises 15-35% by weight of the ethylene copolymer. The composition of claim 22 wherein X comprises 20-35% by weight of the ethylene copolymer. The composition of claim 15 free of X. The composition of claim 15 wherein Y comprises 2-10% by weight of the ethylene copolymer. The composition of claim 25, wherein Y comprises 3-8% by weight of the ethylene copolymer. The composition of claim 15 comprising 0.05-1.0% by weight of an additive selected from the group consisting of calcium carbonate, calcium stearate, stearic acid salts of other metals, and natural and synthetic hydrotalcite, based on the weight of the scrap material. The composition of claim 15, wherein the reinforcing polymer is initially present in the mixture at 5-25% by weight based on the total polymer weight. A product obtained by melt processing the composition of claim 15. A product obtained by melt processing the composition of claim 19. The product of claim 29, which is a container or a film. 31. The product of claim 30, which is a container or film. 33. The product of claim 32, which is a paint can.